DECIGO (DECI-hertz Interferometer Gravitational wave Observatory) is a space gravitational wave antenna which consists of three 1000-km Fabry-Perot interferometers to detect space distortion with the strain sensitivity of δl/l<;10-23 around 0.1 Hz. Before planned launch of DECIGO in 2027, DECIGO pathfinder (DPF) is also planned to launch in 2015 for establishing technical feasibility. In order to obtain such high strain sensitivity, the high frequency stability of δf<;1Hz/√Hz, and the intensity stability of δI/I<;10-8/√Hz at 1Hz, and high power are required for the light source of DECIGO/DPF, whose frequency level is 10 times better than that of LISA project. We have developed a space-borne frequency-stabilized laser around 1μm for DPF. In stead of using an optical cavity, the molecule absorption is chosen as a optical frequency reference because it is less sensitive to external perturbations. In 1μm band, the iodine (I2)-stabilized Nd:YAG lasers with the wavelength of 1064 nm have been studied in many groups as the optical frequency standards.